Accurate alphanumeric and symbol drafting control elements are commonly used in large-scale plotting devices, and a number of exemplary table and drum plotters are currently manufactured by The Gerber Scientific Instrument Company, of Hartford, Connecticut. Such known plotters, while very large and expensive, are most accurate and capable of producing alphanumeric and symbol devices on a platen, as part of a general x and y plotting ability, over very large surface areas.
The present invention is categorically a uniquely portable character/symbol drafting device, for the particular purpose of allowing an individual draftsman to quickly place the instrument upon a drafting surface, and then accurately make an ink trace of alphanumeric and symbol indicia. The present device is primarily a lettering device for producing a single string of characters of symbols, in variable sizes, directly upon any part of a drawing. The present invention performs small-scale ink traces very accurately, since the primary object is to achieve quality reproductions of letter and symbols, without the encumbrance of a large lettering table device. Accordingly, it is the primary object of the present invention to provide a portable unit which will allow any number of character font styles to be easily and accurately reproduced, in response to a keyboard input upon a portable unit. Portability is significantly enhanced in the preferred embodiment by the fact that the electronics, both control and vocabulary memory cartridges, are remotely located in a separate electronics package, with interconnection to the keyboard unit by only a flexible cable. It is a very related subject of the present invention to produce alphanumeric characters and symbols which are characterized with a quality equal to any produced by large-scale plotting devices, and further to be able to quickly change vocabulary font styles, and the outputted letter size for any given font. For this purpose, the present invention teaches a manner of using a replaceable ROM module, containing a complete vocabulary, with each character being digitized according to a uniform matrix. Further objects and advantages of the present invention will become more apparent from the following summary.